Abrasive article with shaped abrasive particles with grooves

ABSTRACT

Abrasive particles comprising shaped abrasive particles each having a sidewall, each of the shaped abrasive particles comprising alpha alumina and having a first face and a second face separated by a sidewall and having a maximum thickness, T; and the shaped abrasive particles further comprising a plurality of grooves on the second face.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of pending priorapplication Ser. No. 12/627,567, now allowed, filed Nov. 30, 2009, whichclaims the benefit of Provisional Application No. 61/138,268, filed Dec.17, 2008, the disclosures of which are incorporated by reference intheir entirety herein.

BACKGROUND

Abrasive particles and abrasive articles made from the abrasiveparticles are useful for abrading, finishing, or grinding a wide varietyof materials and surfaces in the manufacturing of goods. As such, therecontinues to be a need for improving the cost, performance, or life ofthe abrasive particle and/or the abrasive article.

Triangular shaped abrasive particles and abrasive articles using thetriangular shaped abrasive particles are disclosed in U.S. Pat. No.5,201,916 to Berg; U.S. Pat. No. 5,366,523 to Rowenhorst; and U.S. Pat.No. 5,984,988 to Berg. In one embodiment, the abrasive particles' shapecomprised an equilateral triangle. Triangular shaped abrasive particlesare useful in manufacturing abrasive articles having enhanced cut rates.

SUMMARY

Shaped abrasive particles, in general, can have superior performanceover randomly crushed abrasive particles. By controlling the shape ofthe abrasive particle it is possible to control the resultingperformance of the abrasive article. The inventors have discovered thatby making the shaped abrasive particle with a plurality of grooves onone of the shaped abrasive particle's faces, the precursor shapedabrasive particles release much easier from a production tooling havinga plurality of mold cavities used to mold the shaped abrasive particles.Surprisingly, even though the total surface area of the mold cavity isincreased by a plurality of ridges which form the plurality of grooves,the precursor shaped abrasive particles with a plurality of grooves aremuch easier to remove from the mold cavities.

The inventors have also discovered that the grooves on the shapedabrasive particles affect the grinding performance of the shapedabrasive particles when compared to identical shaped abrasive particleswithout the grooves. In particular, the initial cut rate is reduced andthe cut rate tends to increase over time as the shaped abrasiveparticles begin to wear down. Typically, cut rate of an abrasiveparticle tends to decrease over the life of the abrasive particle. Asimilar result occurs with shaped abrasive particles which do notcontain grooves. Thus, the inventors have found that they can manipulatethe cut rate curve for abrasive articles made from the shaped abrasiveparticles by using blends of the shaped abrasive particles withoutgrooves and with grooves to make abrasive articles having an extremelyuniform cut rate over the working life of the abrasive article.

Hence in one embodiment, the invention resides in abrasive particlescomprising shaped abrasive particles each having a sidewall, each of theshaped abrasive particles comprising alpha alumina and having a firstface and a second face separated by a sidewall and having a maximumthickness, T; and the shaped abrasive particles further comprising aplurality of grooves on the second face.

In another embodiment, the invention resides in a production tooling formaking shaped abrasive particles comprising a plurality of moldcavities, the plurality of mold cavities comprising a mold bottomsurface, a mold sidewall, and a height, Hc; the mold bottom surface andthe mold sidewall comprising a polymeric material; and wherein thebottom surface comprises a plurality of ridges.

BRIEF DESCRIPTION OF THE DRAWING

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the presentdisclosure, which broader aspects are embodied in the exemplaryconstruction.

FIG. 1 illustrates a cross sectional view of a mold cavity havingplurality of ridges in the bottom surface.

FIGS. 1A and 1B illustrate various cross sectional embodiments of theridges in FIG. 1.

FIG. 2 illustrates a top view of one embodiment of a shaped abrasiveparticle having grooves.

FIG. 2A illustrates a side view of the shaped abrasive particle of FIG.2.

FIG. 3 illustrates a photomicrograph of the shaped abrasive particlewith grooves.

FIG. 4 illustrates a photomicrograph of another embodiment of the shapedabrasive particle with grooves.

FIG. 5 illustrates another embodiment of the shaped abrasive particlewith grooves.

FIG. 6A illustrates a top view of one embodiment of a shaped abrasiveparticle.

FIG. 6B illustrates a side view the shaped abrasive particle of FIG. 6A.

FIG. 6C illustrates a side view of coated abrasive article made from theshaped abrasive particles of FIG. 6A.

FIG. 7 illustrates a photomicrograph of the shaped abrasive particles.

FIG. 8 illustrates a photomicrograph of the top surface of a coatedabrasive article made from the shaped abrasive particles of FIG. 7.

FIG. 9A illustrates a top view of another embodiment of a shapedabrasive particle.

FIG. 9B illustrates a side view the shaped abrasive particle of FIG. 9A.

FIG. 9C illustrates a side view of coated abrasive article made from theshaped abrasive particles of FIG. 9A.

FIG. 10A illustrates a top view of another embodiment of a shapedabrasive particle.

FIG. 10B illustrates a side view the shaped abrasive particle of FIG.10A.

FIG. 10C illustrates a side view of coated abrasive article made fromthe shaped abrasive particles of FIG. 10A.

FIG. 11 illustrates a graph of Cut Rate and Cumulative Cut for shapedabrasive particles with and without grooves

FIG. 12 illustrates a graph of Cut Rate versus Time for shaped abrasiveparticles with different draft angles.

FIG. 13 illustrates a graph of Total Cut versus Time for shaped abrasiveparticles with different draft angles.

FIG. 14 illustrates a photomicrograph of prior art abrasive particlesmade according to U.S. Pat. No. 5,366,523.

FIG. 15 illustrates a photomicrograph of a cross section of the priorart abrasive particles of FIG. 14.

FIG. 16 illustrates a photomicrograph of a cross section of the priorart abrasive particles of FIG. 14.

FIG. 17 illustrates a photomicrograph of a cross section of a shapedabrasive particle with a sloping sidewall.

Repeated use of reference characters in the specification and drawingsis intended to represent the same or analogous features or elements ofthe disclosure.

DEFINITIONS

As used herein, forms of the words “comprise”, “have”, and “include” arelegally equivalent and open-ended. Therefore, additional non-recitedelements, functions, steps or limitations may be present in addition tothe recited elements, functions, steps, or limitations.

As used herein, the term “abrasive dispersion” means an alpha aluminaprecursor that can be converted into alpha alumina that is introducedinto a mold cavity. The composition is referred to as an abrasivedispersion until sufficient volatile components are removed to bringsolidification of the abrasive dispersion.

As used herein, the term “precursor shaped abrasive particle” means theunsintered particle produced by removing a sufficient amount of thevolatile component from the abrasive dispersion, when it is in the moldcavity, to form a solidified body that can be removed from the moldcavity and substantially retain its molded shape in subsequentprocessing operations.

As used herein, the term “shaped abrasive particle”, means a ceramicabrasive particle with at least a portion of the abrasive particlehaving a predetermined shape that is replicated from a mold cavity usedto form the shaped precursor abrasive particle. Except in the case ofabrasive shards (e.g. as described in U.S. provisional application61/016,965), the shaped abrasive particle will generally have apredetermined geometric shape that substantially replicates the moldcavity that was used to form the shaped abrasive particle. Shapedabrasive particle as used herein excludes abrasive particles obtained bya mechanical crushing operation.

DETAILED DESCRIPTION

Shaped Abrasive Particles with Grooves

Referring to FIG. 1, a portion of a production tool 100 having aplurality of mold cavities 102 is shown. For clarity, a single moldcavity 102 is illustrated. The mold cavity 102 comprises a mold sidewall104 and a mold bottom surface 106, and in one embodiment the mold bottomsurface and the mold sidewall comprised a polymeric material. Thegeometric shape of the mold sidewall 104 forming a perimeter of the moldbottom surface can vary and in one embodiment the geometric shape wasselected to be an equilateral triangle when viewed from the top of eachmold cavity in the production tool such that the mold cavity had threeopposing mold sidewalls. As discussed later herein, other geometricshapes for the mold cavity can be used. The mold sidewall 104 intersectswith the mold bottom surface 106 at a predetermined angle α. Asdiscussed later herein, the grinding of performance of the shapedabrasive particles 20 can be improved by selecting the angle α to bebetween about 95 degrees to about 130 degrees. However, thepredetermined angle α can be 90 degrees or even slightly less than 90degrees since the precursor shaped abrasive particle formed in the moldcavity 102 can shrink during drying and therefore still be removed fromthe mold cavity instead of being trapped.

The mold bottom surface 106 comprises a plurality of ridges 108 risingfrom the mold bottom surface having a predetermined height Hr. In oneembodiment of the invention, the height of the plurality of ridges, Hr,is small as compared to the total height of the mold cavity Hc. Asmentioned, the plurality of ridges 108 have an unexpected benefit ofmaking the precursor shaped abrasive particles much easier to removefrom the mold cavities 102 of the production tooling 100 after theprecursor shaped abrasive particles are dried. This result occurs eventhough the total surface area of the mold cavity is increased by thepresence of the plurality of ridges, which one would expect would makeit harder to remove the precursor shaped abrasive particles. The abilityto easily release the precursor shaped abrasive particles from the moldcavities 102 is an important attribute for making shaped abrasiveparticles on a production line that operates continuously. This benefitis especially important as the speed of the production line isincreased. Retained precursor shaped abrasive particles in theproduction tool “clog up” the production tool, not only reducingthroughput, but also creating issues when attempting to vacuum slot coatthe abrasive dispersion into the production tooling prior to drying theabrasive dispersion in a continuous oven.

It is believed that for the improved release properties to be achieved,the height of the plurality of ridges, Hr, should be smaller whencompared to the total height of the mold cavity Hc. As the height, Hr,approaches the height, Hc, essentially the mold cavity 102 becomessubdivided into several smaller mold cavities and the benefit ofimproved release from the mold cavities can be lost. In variousembodiment of the invention, the height, Hr, of the plurality of ridges108 can be between about 1 micrometer to about 400 micrometers.Furthermore, a percentage ratio of the ridge height to the cavityheight, Hr/Hc (expressed as a percent), can be between 0.1% to about30%, or between 0.1% to about 20%, or between 0.1% to about 10%, orbetween about 0.5% to about 5%.

Additionally, for improved mold release properties, it is believed thatthe cross sectional geometry of the plurality of ridges 108 can beimportant. Referring to FIG. 1A, in one embodiment each ridge 108comprises a first side 110, a second side 112, and a top 114. The firstside 110 and the second side 112 each rise from the mold bottom surface106 at an obtuse angle such that the ridge's cross sectional geometrytapers towards the top 114 forming a truncated triangle. In thisrespect, the ridge's cross sectional geometry also resembles a geartooth or a wedge.

Referring to FIG. 1B, in another embodiment each ridge 108 comprises afirst side 110, and a second side 112. The first side 110 and the secondside 112 each rise from the mold bottom surface 106 at an obtuse anglesuch that the ridge's cross sectional geometry tapers towards the tipforming a triangle. In this respect, the ridge's cross sectionalgeometry also resembles a gear tooth or a wedge. In one embodiment, eachridge had a height, Hr, of 0.0127 mm and the included angle between thefirst side 110 and the second side 112 at the triangle's tip was 45degrees. The mold cavity had a height, Hc, of 0.7112 mm and thepercentage ratio of the ridge height to the cavity height, Hr/Hc was1.79%.

It is believed that by having the ridge's cross section form a truncatedtriangle or triangle, each ridge acts as a wedge during drying thattends to lift the precursor shaped abrasive particle slightly off of themold bottom surface 106 as the precursor shaped abrasive particle isdried. In some embodiments, the precursor shaped abrasive particle isthought to shrink slightly during drying, thereby, the “wedges” loosenthe precursor shaped abrasive particle from the mold bottom surfacemaking it easier to remove the precursor shaped abrasive particle fromthe mold cavity. In other embodiments, the ridge's cross sectionalgeometry can be square, rectangular, hemispherical, convex, parabolic,or other geometric shape.

Since one function of the plurality of ridges 108 is to provide animproved mold release, the spacing and uniformity of the plurality ofridges can be important. In particular, the mold bottom surface 106 ofthe mold cavity should be uniformly provided with ridges to ensure thatportions of the precursor shaped abrasive particle are not “stuck” tothe bottom surface. In one embodiment, the plurality of ridges 108 werecontinuous lines such that the plurality of ridges extended completelyacross the mold bottom surface 106 from one mold sidewall to theopposing mold sidewall of the triangular mold cavity. The plurality ofridges had a triangular cross section as described for FIG. 1B andcomprised parallel lines that were spaced approximately every 0.277 mm.

In various embodiments of the invention, a percent spacing between eachridge can be between about 1% to about 50%, 1% to 40%, 1% to 30%, 1% to20%, or 5% to 20% of a face dimension such as the length of one of theedges of the shaped abrasive particle. In one embodiment, an equilateraltriangle having a side length at the mold bottom surface 106 of 2.54millimeters and having 8 ridges per mold cavity at a spacing of 277micrometers had a percent spacing between each ridge of 10.9%. In otherembodiments of the invention the number of ridges in the mold bottomsurface can be between 1 and about 100, about 2 to about 50, or about 4to about 25.

The plurality of ridges can be placed onto the mold bottom surface inarcuate lines, straight lines, concentric geometric patterns such asnesting triangles, or cross-hatched lines having regular or irregularspacing. The plurality of ridges can be parallel to each other orintersecting. Combinations of various patterns can be used.

In other embodiments of the invention, the plurality of ridges can be inthe form of discrete line segments that are placed at intervals alongthe bottom surface such that the plurality of ridges do not extendcontinuously between the opposing mold sidewalls. Alternatively, theline segmented plurality of ridges can be shortened considerably suchthat the bottom surface comprises a plurality of truncated pyramidsevenly spaced into a grid pattern such that the bottom surface resemblesa waffle iron griddle. Other discrete geometric ridge shapes can beplaced onto the bottom surface to provide the surface with a dimpledpattern to improve its release characteristics.

Referring now to FIGS. 2 and 2A, a shaped abrasive particle 20 having aplurality of grooves 116 made from the mold cavity 102 of FIG. 1 isillustrated. The material from which the shaped abrasive particle 20with grooves is made comprises alpha alumina. Alpha alumina particlescan be made from a dispersion of aluminum oxide monohydrate that isgelled, molded to shape, dried to retain the shape, calcined, and thensintered as discussed later herein. The shaped abrasive particle's shapeis retained without the need for a binder to form an agglomeratecomprising abrasive particles in a binder that are then formed into ashaped structure.

In general, the shaped abrasive particles 20 with grooves 116 comprisethin bodies having a first face 24, and a second face 26 and having athickness T. The first face 24 and the second face 26 are connected toeach other by a sidewall 22 and the sidewall may be angled to form asloping sidewall 22 as discussed later herein by using a mold cavityhaving an angle α greater than 90 degrees between the mold sidewall andthe mold bottom surface. The sidewall can be minimized for shapedabrasive particles with faces that taper to a thin edge or point insteador having a thicker sidewall.

In some embodiments, the first face 24 is substantially planar, thesecond face 26 is substantially planar, or both faces are substantiallyplanar. Alternatively, the faces could be concave or convex as discussedin more detail in copending U.S. application Ser. No. 12/336,961entitled “Dish-Shaped Abrasive Particles With A Recessed Surface”, filedon Dec. 17, 2008. Additionally, an opening or aperture through the facescould be present as discussed in more detail in copending U.S.application Ser. No. 12/337,112 entitled “Shaped Abrasive Particles WithAn Opening”, filed on Dec. 17, 2008. As discussed in the referencedapplications, including either a recessed face or an opening in theshaped abrasive particles has been found to significantly enhance thegrinding performance.

In one embodiment, the first face 24 and the second face 26 aresubstantially parallel to each other. In other embodiments, the firstface 24 and second face 26 can be nonparallel such that one face issloped with respect to the other face and imaginary lines tangent toeach face would intersect at a point. The sidewall 22 of the shapedabrasive particle 20 with grooves 116 can vary and it generally formsthe perimeter 29 of the first face 24 and the second face 26. In oneembodiment, the perimeter 29 of the first face 24 and second face 26 isselected to be a geometric shape, and the first face 24 and the secondface 26 are selected to have the same geometric shape, although, theydiffer in size with one face being larger than the other face. In oneembodiment, the perimeter 29 of first face 24 and the perimeter 29 ofthe second face 26 was a triangular shape that is illustrated.

Referring to FIG. 2A, a draft angle α between the second face 26 and thesidewall 22 of the shaped abrasive particle 20 can be varied to changethe relative sizes of each face. In various embodiments of theinvention, the draft angle α can be 90 degrees, or between approximately95 degrees to approximately 130 degrees, or between about 95 degrees toabout 125 degrees, or between about 95 degrees to about 120 degrees, orbetween about 95 degrees to about 115 degrees, or between about 95degrees to about 110 degrees, or between about 95 degrees to about 105degrees, or between about 95 degrees to about 100 degrees. As will beseen in the Examples, specific ranges for the draft angle α have beenfound to produce surprising increases in the grinding performance ofcoated abrasive articles made from the shaped abrasive particles.

The shaped abrasive particles with grooves can be used to make coatedabrasive articles as discussed later herein. If the shaped abrasiveparticles 20 with grooves 116 have a draft angle α greater than 90degrees (sloping sidewall), the majority of the shaped abrasiveparticles 20 with grooves will be tipped or leaning to one side whenmaking a coated abrasive article. As discussed later herein, it isbelieved that this results in improved grinding performance.

To further optimize the leaning orientation, the shaped abrasiveparticles with grooves and a sloping sidewall can be applied in thebacking in an open coat abrasive layer. A closed coat abrasive layer isdefined as the maximum weight of abrasive particles or a blend ofabrasive particles that can be applied to a make coat of an abrasivearticle in a single pass through the maker. An open coat is an amount ofabrasive particles or a blend of abrasive particles, weighing less thanthe maximum weight in grams that can be applied, that is applied to amake coat of a coated abrasive article. An open coat abrasive layer willresult in less than 100% coverage of the make coat with abrasiveparticles thereby leaving open areas and a visible resin layer betweenthe particles as best seen in FIG. 8. In various embodiments of theinvention, the percent open area in the abrasive layer can be betweenabout 10% to about 90% or between about 30% to about 80%.

It is believed that if too many of the shaped abrasive particles withgrooves and a sloping sidewall are applied to the backing, insufficientspaces between the particles will be present to allow for the particlesto lean or tip prior to curing the make and size coats. In variousembodiments of the invention, greater than 50, 60, 70, 80, or 90 percentof the shaped abrasive particles in the coated abrasive article havingan open coat abrasive layer are tipped or leaning.

Referring now to FIG. 3, a photomicrograph of shaped abrasive particles20 with grooves 116 and a sloping sidewall is shown. In FIG. 3 the draftangle α is approximately 98 degrees and the shaped abrasive particlescomprised an equilateral triangle. The sides of each triangle measuredapproximately 1.6 mm at the perimeter of the larger first face 24. Thedish-shaped abrasive particles had a recessed first face 24 as seen bynoting the varying sidewall thickness and the fact that the shapedabrasive particles are resting mainly on the tips or corners of thetriangles.

Referring now to FIG. 4, a photomicrograph of shaped abrasive particles20 with grooves 116 is shown. In FIG. 4 the draft angle α of the moldwas 98 degrees and the shaped abrasive particles comprised anequilateral triangle. The sides of each triangle measured approximately1.6 mm at the perimeter of the larger first face 24. The dish-shapedabrasive particles had a concave first face 24 and a convex second face26 (originally formed on the mold bottom surface). More information ondish-shaped abrasive particles having either a recessed or concave faceis disclosed in U.S. application Ser. No. 12/336,961 mentioned above.

The grooves 116 on the second face 26 are formed by the plurality ofridges 108 on the mold bottom surface. As such, the pattern of grooveson the second face 26 will replicate any of the patterns discussed abovefor the ridges. In one embodiment, the plurality of grooves comprisesparallel lines extending completely across the second face andintersecting with the perimeter along an edge at a 90 degree angle. Thegrooves cross sectional geometry was a triangle, or can be the othergeometries as discussed above.

In various embodiments of the invention, the depth, D, of the pluralityof grooves 116 can between about 1 and 400 micrometers. Furthermore, apercentage ratio of the groove depth, D, to the shaped abrasiveparticle's maximum thickness, T, (D/T expressed as a percent) can bebetween 0.1% to about 30%, or between 0.1% to about 20%, or between 0.1%to about 10%, or between about 0.5% to about 5%.

The plurality of grooves placed onto the shaped abrasive particle as aresult of improving the release capability of the production toolingsurprisingly have been found to affect grinding performance of theresulting shaped abrasive particles with grooves. This result occurseven though the groove's depth, D, can be small compared to the shapedabrasive particle's maximum thickness, T. It is unknown whether thisresult occurs due to increased fracturing of the shaped abrasiveparticles during use along the grooves, which can form fresh new sharpedges, or because the grooves themselves without fracturing of theshaped abrasive particle provide fresh sharp edges and a slightlyreduced wear flat once the shaped abrasive particle with grooves is wornthrough to expose a particular groove. Since there are multiple groovesper shaped abrasive particle, there are multiple opportunities for theshaped abrasive particle with grooves to re-sharpen itself.

As will be discussed in more detail in the Examples, the plurality ofgrooves in one embodiment tended to reduce the shaped abrasiveparticle's initial cut rate and then increase cut rate as the abrasivearticle was used. Similar size shaped abrasive particles without groovestended to have a higher initial cut rate and then decrease in cut rateas the abrasive article was used. By blending the shaped abrasiveparticles with grooves with shaped abrasive particles without grooves,the cut rate of the abrasive article during initial use and later usecan be made more uniform. A uniform cut rate is often important toconsumers of abrasive articles in order to prevent having to readjustproduction machinery as the abrasive wears while making standardizedparts. In various embodiments, at least 5, 10, 15, 20, 25, 30, 35, 40,45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95 percent by weight of theshaped abrasive particles with grooves can be mixed with shaped abrasiveparticles without grooves. In one embodiment, a 50%-50% mixture ofequilateral triangle shaped abrasive particles with the plurality ofgrooves and equilateral triangle shaped abrasive particles without theplurality of grooves was found to provide a very uniform cut rate versustime. In various embodiments of the invention, a blend of the shapedabrasive particles can comprise about 40% to about 60% of the shapedabrasive particles with the plurality of grooves and about 40% to about60% of the shaped abrasive particles without the plurality of grooves.

Referring now to FIG. 5 another embodiment for the plurality of grooveson the second face 26 is illustrated. The plurality of grooves compriseda cross hatch pattern of intersecting parallel lines extendingcompletely across the second face 26. A first set of 17 parallel linesintersected one edge of the perimeter at a 90 degree angle having apercent spacing of 6.25% of the edge length of the triangle, and asecond set of 17 parallel lines intersected a second edge of theperimeter at a 90 degree angle having a percent spacing of 6.25%creating the cross hatch pattern and forming a plurality of raiseddiamonds in the second face. In various embodiments, the cross hatchpattern can use intersecting parallel or non-parallel lines, variouspercent spacing between the lines, arcuate intersecting lines, orvarious cross-sectional geometries of the grooves.

Shaped Abrasive Particle with a Sloping Sidewall

Referring to FIGS. 6A, 6B, and 6C an exemplary shaped abrasive particle20 with a sloping sidewall 22 is illustrated. In the followingdiscussion, any embodiments of the shaped abrasive particles with asloping sidewall (draft angle α greater than 90 degrees) can be combinedwith any of the embodiments of the shaped abrasive particles withgrooves 116 as discussed above. The material from which the shapedabrasive particle 20 with a sloping sidewall 22 is made comprises alphaalumina. Alpha alumina particles can be made from a dispersion ofaluminum oxide monohydrate that is gelled, molded to shape, dried toretain the shape, calcined, and then sintered as discussed herein later.

In general, the shaped abrasive particles 20 with a sloping sidewall 22comprise thin bodies having a first face 24, and a second face 26 andhaving a thickness t. The first face 24 and the second face 26 areconnected to each other by at least one sloping sidewall 22. In someembodiments, more than one sloping sidewall 22 can be present and theslope or angle for each sloping sidewall 22 may be the same as shown inFIG. 6A or different as shown in FIG. 9A.

In some embodiments, the first face 24 is substantially planar, thesecond face 26 is substantially planar, or both faces are substantiallyplanar. Alternatively, the faces could be concave or convex as discussedin more detail in copending U.S. application Ser. No. 12/336,961entitled “Dish-Shaped Abrasive Particles With A Recessed Surface”, filedon Dec. 17, 2008. Additionally, an opening or aperture through the facescould be present as discussed in more detail in copending U.S.application Ser. No. 12/337,112 entitled “Shaped Abrasive Particles WithAn Opening”, filed on Dec. 17, 2008.

In one embodiment, the first face 24 and the second face 26 aresubstantially parallel to each other. In other embodiments, the firstface 24 and second face 26 can be nonparallel such that one face issloped with respect to the other face and imaginary lines tangent toeach face would intersect at a point. The sloping sidewall 22 of theshaped abrasive particle 20 with a sloping sidewall 22 can vary and itgenerally forms the perimeter 29 of the first face 24 and the secondface 26. In one embodiment, the perimeter 29 of the first face 24 andsecond face 26 is selected to be a geometric shape, and the first face24 and the second face 26 are selected to have the same geometric shape,although, they differ in size with one face being larger than the otherface. In one embodiment, the perimeter 29 of first face 24 and theperimeter 29 of the second face 26 was a triangular shape that isillustrated.

Referring to FIGS. 6B and 6C, a draft angle α between the second face 26and the sloping sidewall 22 of the shaped abrasive particle 20 can bevaried to change the relative sizes of each face. In various embodimentsof the invention, the draft angle α can be between approximately 95degrees to approximately 130 degrees, or between about 95 degrees toabout 125 degrees, or between about 95 degrees to about 120 degrees, orbetween about 95 degrees to about 115 degrees, or between about 95degrees to about 110 degrees, or between about 95 degrees to about 105degrees, or between about 95 degrees to about 100 degrees. As will beseen in the Examples, specific ranges for the draft angle α have beenfound to produce surprising increases in the grinding performance ofcoated abrasive articles made from the shaped abrasive particles with asloping sidewall.

Referring now to FIG. 6C, a coated abrasive article 40 is shown having afirst major surface 41 of a backing 42 covered by an abrasive layer. Theabrasive layer comprises a make coat 44, and a plurality of shapedabrasive particles 20 with a sloping sidewall 22 attached to the backing42 by the make coat 44. A size coat 46 is applied to further attach oradhere the shaped abrasive particles 20 with a sloping sidewall 22 tothe backing 42.

As seen, the majority of the shaped abrasive particles 20 with a slopingsidewall 22 are tipped or leaning to one side. This results in themajority of the shaped abrasive particles 20 with a sloping sidewall 22having an orientation angle β less than 90 degrees relative to the firstmajor surface 41 of the backing 42. This result is unexpected since theelectrostatic coating method of applying the shaped abrasive particleswith a sloping sidewall tends to originally orientate the particles atan orientation angle β of 90 degrees when they are first applied to thebacking. The electrostatic field tends to align the particles verticallywhen applying them to the backing that is located above the shapedabrasive particles with a sloping sidewall. Furthermore, theelectrostatic field tends to accelerate and drive the particles into themake coat at the 90 degree orientation. At some point after the web isturned over, either before or after the size coat 46 is applied, theparticles under the force of gravity or the surface tension of the makeand/or size coat tend to lean over and come to rest on the slopingsidewall 22. It is believed that sufficient time in the process ofmaking the coated abrasive article is present for the shaped abrasiveparticles to lean over and become attached to the make coat by thesloping sidewall 22 before the make coat and size coat cure and hardenpreventing any further rotation. As seen, once the shaped abrasiveparticles with a sloping sidewall are applied and allowed to lean, thevery tips 48 of the shaped abrasive particles have generally the sameheight, h.

To further optimize the leaning orientation, the shaped abrasiveparticles with a sloping sidewall are applied in the backing in an opencoat abrasive layer. A closed coat abrasive layer is defined as themaximum weight of abrasive particles or a blend of abrasive particlesthat can be applied to a make coat of an abrasive article in a singlepass through the maker. An open coat is an amount of abrasive particlesor a blend of abrasive particles, weighing less than the maximum weightin grams that can be applied, that is applied to a make coat of a coatedabrasive article. An open coat abrasive layer will result in less than100% coverage of the make coat with abrasive particles thereby leavingopen areas and a visible resin layer between the particles as best seenin FIG. 8. In various embodiments of the invention, the percent openarea in the abrasive layer can be between about 10% to about 90% orbetween about 30% to about 80%.

It is believed that if too many of the shaped abrasive particles with asloping sidewall are applied to the backing, insufficient spaces betweenthe particles will be present to allow from them to lean or tip prior tocuring the make and size coats. In various embodiments of the invention,greater than 50, 60, 70, 80, or 90 percent of the shaped abrasiveparticles in the coated abrasive article having an open coat abrasivelayer are tipped or leaning having an orientation angle β of less than90 degrees.

Without wishing to be bound by theory, it is believed that anorientation angle β less than 90 degrees results in enhanced cuttingperformance of the shaped abrasive particles with a sloping sidewall.Surprisingly, this result tends to occur regardless of the shapedabrasive particles' rotational orientation about the Z axis within thecoated abrasive article. While FIG. 6C is idealized to show all theparticles aligned in the same direction, an actual coated abrasive discwould have the particles randomly distributed and rotated as best seenin FIG. 8. Since the abrasive disc is rotating and the shaped abrasiveparticles are randomly distributed, some shaped abrasive particles willbe driven into the workpiece at an orientation angle β of less than 90degrees with the workpiece initially striking the second face 26 while aneighboring shaped abrasive particle could be rotated exactly 180degrees with the workpiece striking backside of the shaped abrasiveparticle and the first face 24. With a random distribution of theparticles and the rotation of the disc, less than half of the shapedabrasive particles could have the workpiece initially striking thesecond face 26 instead of the first face 24. However, for an abrasivebelt having a defined direction of rotation and a defined point ofcontact with the workpiece, it may be possible to align the shapedabrasive particles with a sloping sidewall on the belt to ensure thateach shaped abrasive particle runs at an orientation angle β of lessthan 90 degrees and that the workpiece is driven into the second face 26first as idealized in FIG. 6C. In various embodiments of the invention,the orientation angle β for at least a majority of the shaped abrasiveparticles with a sloping sidewall in an abrasive layer of a coatedabrasive article can be between about 50 degrees to about 85 degrees, orbetween about 55 degrees to about 85 degrees, or between about 60degrees to about 85 degrees, or between about 65 degrees to about 85degrees, or between about 70 degrees to about 85 degrees, or betweenabout 75 degrees to about 85 degrees, or between about 80 degrees toabout 85 degrees.

Referring now to FIGS. 7 and 8, photomicrographs of shaped abrasiveparticles 20 with a sloping sidewall 22 are shown. In FIG. 7 the draftangle α is approximately 120 degrees and the shaped abrasive particlescomprised an equilateral triangle. The sides of each triangle measuredapproximately 1.6 mm at the perimeter of the larger first face 24. Theshaped abrasive particles had a thickness of approximately 0.38 mm. Thesurface of the resulting coated abrasive disc made from the shapedabrasive particles of FIG. 7 is shown in FIG. 8. As seen, the majorityof the shaped abrasive particles are resting in the make coat on one ofthe sloping sidewalls. The orientation angle β for the majority of theshaped abrasive particles with a sloping sidewall in the abrasive layerof the coated abrasive article in FIG. 3 is approximately 60 degrees.

Referring to FIGS. 9A-C, a second embodiment of the shaped abrasiveparticle 20 with a sloping sidewall 22 is illustrated. The material fromwhich the shaped abrasive particle 20 with a sloping sidewall 22 is madecomprises alpha alumina. Alpha alumina particles can be made from adispersion of aluminum oxide monohydrate that is gelled, molded toshape, dried to retain the shape, calcined, and then sintered asdiscussed herein later.

In general, the shaped abrasive particles 20 with a sloping sidewall 22comprise thin bodies having a first face 24, and a second face 26 andhaving a thickness t. The first face 24 and the second face 26 areconnected to each other by at least a first sloping sidewall 50 having afirst draft angle 52 and by a second sloping sidewall 54 having a seconddraft angle 56, which is selected to be a different value from the firstdraft angle. In the illustrated embodiment, the first and second facesare also connected by a third sloping sidewall 58 having a third draftangle 60, which is a different value from either of the other two draftangles.

In the illustrated embodiment, the first, second and third draft anglesare all different values from each other. For example, the first draftangle 52 could be 120 degrees, the second draft angle 56 could be 110degrees, and the third draft angle 60 could be 100 degrees. Theresulting coated abrasive article 40, as shown in FIG. 4C, made from theshaped abrasive particles with the three different draft angles willtend to have an even distribution of shaped abrasive particles landingon each of the three different sloping sidewalls. As such, the coatedabrasive article will tend to have three distinct heights for the tips48 of the shaped abrasive particles from the backing. The first slopingsidewall 50 contacting the make coat with the largest draft angle willhave the lowest tip height, h1, the second sloping sidewall 54 with theintermediate draft angle will have an intermediate tip height, h2, andthe third sloping sidewall, 58, with the smallest draft angle will havethe highest tip height, h3. As a result, the coated abrasive articlewill possess shaped abrasive particles having three distinct orientationangles β relative to the backing and three distinct tip heights. It isbelieved that such a coated abrasive article will possess more uniformcutting performance as the abrasive article wears due to the unusedshorter tips of the shaped abrasive particles coming into contact withthe workpiece as the taller tips of the shaped abrasive particles tendto wear down and dull.

In some embodiments, the first face 24 is substantially planar, thesecond face 26 is substantially planar, or both faces are substantiallyplanar. Alternatively, the faces could be concave or convex as discussedin more detail in copending U.S. application Ser. No. 12/336,961entitled “Dish-Shaped Abrasive Particles With A Recessed Surface”, filedon Dec. 17, 2008. Additionally, an opening or aperture through the facescould be present as discussed in more detail in copending U.S.application Ser. No. 12/337,112 entitled “Shaped Abrasive Particles WithAn Opening”, filed on Dec. 17, 2008.

In one embodiment, the first face 24 and the second face 26 aresubstantially parallel to each other. In other embodiments, the firstface 24 and second face 26 can be nonparallel such that one face issloped with respect to the other face and imaginary lines tangent toeach face would intersect at a point. The first, second, and thirdsloping sidewalls of the shaped abrasive particle 20 with a slopingsidewall 22 can vary and they generally form the perimeter 29 of thefirst face 24 and the second face 26. In one embodiment, the perimeter29 of the first face 24 and the second face 26 is selected to be ageometric shape, and the first face 24 and the second face 26 areselected to have the same geometric shape, although, they differ in sizewith one face being larger than the other face. In one embodiment, theperimeter 29 of first face 24 and the perimeter 29 of the second face 26was a triangular shape that is illustrated.

Referring to FIGS. 9B and 9C, the first, second, and third, draft anglesbetween the second face 26 and the respective sloping sidewall of theshaped abrasive particle 20 can be varied with at least two of the draftangles being different values, and desirably all three being differentvalues. In various embodiments of the invention, the first draft angle,the second draft angle, and the third draft angle can be between about95 degrees to about 130 degrees, or between about 95 degrees to about125 degrees, or between about 95 degrees to about 120 degrees, orbetween about 95 degrees to about 115 degrees, or between about 95degrees to about 110 degrees, or between about 95 degrees to about 105degrees, or between about 95 degrees to about 100 degrees.

Referring now to FIG. 9C, a coated abrasive article 40 is shown having afirst major surface 41 of a backing 42 covered by an abrasive layer. Theabrasive layer comprises a make coat 44, and a plurality of shapedabrasive particles 20 with either the first, the second, or the thirdsloping sidewall attached to the backing 42 by the make coat 44. A sizecoat 46 is applied to further attach or adhere the shaped abrasiveparticles 20 with a sloping sidewall 22 to the backing 42.

As seen, the majority of the shaped abrasive particles 20 with a slopingsidewall 22 are tipped or leaning to one side. This results in themajority of the shaped abrasive particles 20 with a sloping sidewall 22having an orientation angle β less than 90 degrees relative to the firstmajor surface 41 of the backing 42 as previously discussed for the firstembodiment.

To further optimize the leaning orientation, the shaped abrasiveparticles with a sloping sidewall are applied in the backing in an opencoat abrasive layer. An open coat abrasive layer will result in lessthan 100% coverage of the make coat with abrasive particles therebyleaving open areas and a visible resin layer between the abrasiveparticles as best seen in FIG. 8. In various embodiments of theinvention, the percent open area in the abrasive layer can be betweenabout 10% to about 90% or between about 30% to about 80%.

It is believed that if too many of the shaped abrasive particles with asloping sidewall are applied to the backing, insufficient spaces betweenthe shaped abrasive particles will be present to allow for them to leanor tip prior to curing the make and size coats. In various embodimentsof the invention, greater than 50, 60, 70, 80, or 90 percent of theshaped abrasive particles in the coated abrasive article having an opencoat abrasive layer are tipped or leaning having an orientation angle βof less than 90 degrees.

Without wishing to be bound by theory, it is believed that anorientation angle β of less than 90 degrees results in enhanced cuttingperformance of the shaped abrasive particles with a sloping sidewall aspreviously discussed. In various embodiments of the invention, theorientation angle β for at least a majority of the shaped abrasiveparticles with a sloping sidewall in an abrasive layer of a coatedabrasive article can be between about 50 degrees to about 85 degrees, orbetween about 55 degrees to about 85 degrees, or between about 60degrees to about 85 degrees, or between about 65 degrees to about 85degrees, or between about 70 degrees to about 85 degrees, or betweenabout 75 degrees to about 85 degrees, or between about 80 degrees toabout 85 degrees.

Referring now to FIGS. 10A-B a third embodiment of the invention isshown. In this embodiment, the sloping sidewall 22 is defined by aradius, R, instead of the draft angle α for the embodiment shown inFIGS. 6A-6C. A sloping sidewall 22 defined by a radius, R, has also beenfound to result in the shaped abrasive particles 20 tipping or leaningwhen forming a coated abrasive article as shown in FIG. 10C. Grindingtests have shown that shaped abrasive particles comprising anequilateral triangle with the sides of each triangle measuringapproximately 1.6 mm at the perimeter of the larger first face 24, andhaving a thickness of approximately 0.38 mm, have the same cutperformance with a draft angle of 120 degrees or a radius, R, of 0.51mm. In various embodiment of the invention, the radius, R, can bebetween about 0.5 to about 2 times the thickness, t, of the shapedabrasive particle.

As with the second embodiment, the radius, R, can be varied for each ofthe sidewalls to result in shaped abrasive particles leaning or tippingto varying degrees in the coated abrasive article.

It is believed that if too many of the shaped abrasive particles with asloping sidewall are applied to the backing, insufficient spaces betweenthe shaped abrasive particles will be present to allow for them to leanor tip prior to curing the make and size coats. In various embodimentsof the invention, greater than 50, 60, 70, 80, or 90 percent of theshaped abrasive particles in the coated abrasive article having an opencoat abrasive layer are tipped or leaning having an orientation angle βof less than 90 degrees.

For either the first embodiment, the second embodiment, or the thirdembodiment, the shaped abrasive particles 20 with a sloping sidewall 22can have various three-dimensional shapes. The geometric shape of theperimeter 29 can be triangular, rectangular, circular, elliptical,star-shaped or that of other regular or irregular polygons. In oneembodiment, an equilateral triangle is used and in another embodiment,an isosceles triangle is used. For the purpose of this disclosure, asubstantially triangular shape also includes three-sided polygonswherein one or more of the sides can be arcuate and/or the tips of thetriangle can be arcuate.

Additionally, the various sloping sidewalls of the shaped abrasiveparticles can have the same draft angle or different draft angles.Furthermore, a draft angle of 90 degrees can be used on one or moresidewalls as long as one of the sidewalls is a sloping sidewall having adraft angle of about 95 degrees or greater.

The shaped abrasive particles 20 with a sloping sidewall can havevarious volumetric aspect ratios. The volumetric aspect ratio is definedas the ratio of the maximum cross sectional area passing through thecentroid of a volume divided by the minimum cross sectional area passingthrough the centroid. For some shapes, the maximum or minimum crosssectional area may be a plane tipped, angled, or tilted with respect tothe external geometry of the shape. For example, a sphere would have avolumetric aspect ratio of 1.000 while a cube will have a volumetricaspect ratio of 1.414. A shaped abrasive particle in the form of anequilateral triangle having each side equal to length A and a uniformthickness equal to A will have a volumetric aspect ratio of 1.54, and ifthe uniform thickness is reduced to 0.25 A, the volumetric aspect ratiois increased to 2.64. It is believed that shaped abrasive particleshaving a larger volumetric aspect ratio have enhanced cuttingperformance. In various embodiments of the invention, the volumetricaspect ratio for the shaped abrasive particles with a sloping sidewallcan be greater than about 1.15, or greater than about 1.50, or greaterthan about 2.0, or between about 1.15 to about 10.0, or between about1.20 to about 5.0, or between about 1.30 to about 3.0.

The shaped abrasive particles with a sloping sidewall can have a muchsmaller radius of curvature at the points or corners of the shapedabrasive particles. The equilateral triangular shaped abrasive particlesdisclosed in U.S. Pat. No. 5,366,523 to Rowenhorst et al. and picturedin FIG. 14, had a radius of curvature for the points of the triangle(measured from one side around the point to the next side) of 103.6microns for the average tip radius. The radius of curvature can bemeasured from a polished cross-section of the first or second face usingimage analysis such as a Clemex Image Analysis program interfaced withan inverted light microscope or other suitable image analysis software.The radius of curvature for each triangular apex can be estimated bydefining three points at each apex when viewed in cross section at 100×magnification. A point is placed at the start of the tip's curve wherethere is a transition from the straight edge to the start of a curve, atthe apex of the tip, and at the transition from the curved tip back to astraight edge. The image analysis software then draws an arc defined bythe three points (start, middle, and end of the curve) and calculates aradius of curvature. The radius of curvature for at least 30 apexes aremeasured and averaged to determine the average tip radius. The shapedabrasive particles made by the current method are much more preciselymade as best seen by comparing FIG. 7 to FIG. 14. As such, the averagetip radius for the shaped abrasive particles is much less. The averagetip radius for shaped abrasive particles made according to the presentdisclosure has been measured to be less than 19.2 microns. In variousembodiments of the invention, the average tip radius can be less than 75microns, or less than 50 microns, or less than 25 microns. It isbelieved that a sharper tip promotes more aggressive cutting an improvedfracturing of the shaped abrasive particles during use.

In addition to having a sharper tip, the shaped abrasive particles canhave a much more precisely defined sidewall. Referring now to FIGS. 15and 16, photomicrographs of polished cross sections taken perpendicularthrough the faces of the prior art shaped abrasive particles of FIG. 14are shown. As seen, the sidewall (top surface) tends to be eitherconcave or convex and is not uniformly planar. Depending on where youtake the cross section, the same sidewall may transition from one shapeto another. Referring to FIG. 16, in the foreground the sidewall isconvex while in the background it is concave.

Referring to FIG. 17, a polished cross section taken perpendicularthrough the faces of a shaped abrasive particle with a sloping sidewallhaving a 98 degree draft angle is shown. The first face 24 (right handvertical surface) is concave as disclosed in U.S. application Ser. No.12/336,961, entitled ”Dish-Shaped Abrasive Particles with a RecessedSurface⇄, filed Dec. 17, 2008. A concave surface is thought to enhancegrinding performance by removing more material during use similar to ascoop, spoon, or hollow ground chisel blade. The second face 26 issubstantially planar (left hand vertical surface). Finally, the sidewall(top surface) is uniformly planar. By uniformly planar it is meant thatthe sidewall does not have areas that are convex from one face to theother face, or areas that are concave from one face to the other faceand at least 50%, or at least 75%, or at least 85% or more of thesidewall surface is planar. As seen in the cross section, when thesidewall is cut at a 90 degree angle and polished, a substantiallylinear edge appears (where the top sidewall surface meets the cut crosssection's front surface). The uniformly planar sidewall would typicallyhave that substantially linear edge at substantially all cross sectionalplanes along the length of the sidewall. The uniformly planar sidewallprovides better defined (sharper) edges where the sidewall intersectswith the first face and the second face, and this is also thought toenhance grinding performance.

Shaped abrasive particles 20 with a sloping sidewall 22 and/or grooves116 made according to the present disclosure can be incorporated into anabrasive article, or used in loose form. Abrasive particles aregenerally graded to a given particle size distribution before use. Suchdistributions typically have a range of particle sizes, from coarseparticles to fine particles. In the abrasive art this range is sometimesreferred to as a “coarse”, “control”, and “fine” fractions. Abrasiveparticles graded according to abrasive industry accepted gradingstandards specify the particle size distribution for each nominal gradewithin numerical limits. Such industry accepted grading standards (i.e.,abrasive industry specified nominal grade) include those known as theAmerican National Standards Institute, Inc. (ANSI) standards, Federationof European Producers of Abrasive Products (FEPA) standards, andJapanese Industrial Standard (JIS) standards.

ANSI grade designations (i.e., specified nominal grades) include: ANSI4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI 40, ANSI 50, ANSI 60,ANSI 80, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI 220, ANSI 240,ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600. FEPA gradedesignations include P8, P12, P16, P24, P36, P40, P50, P60, P80, P100,P120, P150, P180, P220, P320, P400, P500, P600, P800, P1000, and P1200.JIS grade designations include JIS8, JIS12, JIS16, JIS24, JIS36, JIS46,JIS54, JIS60, JIS80, JIS100, JIS150, JIS180, JIS220, JIS240, JIS280,JIS320, JIS360, JIS400, JIS600, JIS800, JIS1000, JIS1500, JIS2500,JIS4000, JIS6000, JIS8000, and JIS10,000.

Alternatively, the shaped abrasive particles 20 with a sloping sidewall22 and/or grooves 116 can graded to a nominal screened grade usingU.S.A. Standard Test Sieves conforming to ASTM E-11 “StandardSpecification for Wire Cloth and Sieves for Testing Purposes.” ASTM E-11proscribes the requirements for the design and construction of testingsieves using a medium of woven wire cloth mounted in a frame for theclassification of materials according to a designated particle size. Atypical designation may be represented as −18+20 meaning that the shapedabrasive particles 20 pass through a test sieve meeting ASTM E-11specifications for the number 18 sieve and are retained on a test sievemeeting ASTM E-11 specifications for the number 20 sieve. In oneembodiment, the shaped abrasive particles 20 with a sloping sidewall 22have a particle size such that most of the particles pass through an 18mesh test sieve and can be retained on a 20, 25, 30, 35, 40, 45, or 50mesh test sieve. In various embodiments of the invention, the shapedabrasive particles 20 with a sloping sidewall 22 can have a nominalscreened grade comprising: −18+20, −20+25, −25+30, −30+35, −35+40,−40+45, −45+50, −50+60, −60+70, −70+80, −80+100, −100+120, −120+140,−140+170, −170+200, −200+230, −230+270, −270+325, −325+400, −400+450,−450+500, or −500+635.

In one aspect, the present disclosure provides a plurality of shapedabrasive particles having an abrasives industry specified nominal gradeor nominal screened grade, wherein at least a portion of the pluralityof abrasive particles are shaped abrasive particles 20 with a slopingsidewall 22 and/or grooves 116. In another aspect, the disclosureprovides a method comprises grading the shaped abrasive particles 20made according to the present disclosure to provide a plurality ofshaped abrasive particles 20 having an abrasives industry specifiednominal grade or a nominal screened grade.

If desired, the shaped abrasive particles 20 having an abrasivesindustry specified nominal grade or a nominal screened grade can bemixed with other known abrasive or non-abrasive particles. In someembodiments, at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,70, 75, 80, 85, 90, 95, or even 100 percent by weight of the pluralityof abrasive particles having an abrasives industry specified nominalgrade or a nominal screened grade are shaped abrasive particles 20 madeaccording to the present disclosure, based on the total weight of theplurality of abrasive particles.

Particles suitable for mixing with the shaped abrasive particles 20 witha sloping sidewall 22 and/or grooves 116 include conventional abrasivegrains, diluent grains, or erodable agglomerates, such as thosedescribed in U.S. Pat. Nos. 4,799,939 and 5,078,753. Representativeexamples of conventional abrasive grains include fused aluminum oxide,silicon carbide, garnet, fused alumina zirconia, cubic boron nitride,diamond, and the like. Representative examples of diluent grains includemarble, gypsum, and glass. Blends of differently shaped abrasiveparticles 20 with a sloping sidewall 22 (triangles and squares forexample) or blends of shaped abrasive particles 20 with different draftangles (for example particles having an 98 degree draft angle mixed withparticles having a 120 degree draft angle) can be used in the articlesof this invention.

The shaped abrasive particles 20 may also have a surface coating.Surface coatings are known to improve the adhesion between abrasivegrains and the binder in abrasive articles or can be used to aid inelectrostatic deposition of the shaped abrasive particles 20. Suchsurface coatings are described in U.S. Pat. Nos. 5,213,591; 5,011,508;1,910,444; 3,041,156; 5,009,675; 5,085,671; 4,997,461; and 5,042,991.Additionally, the surface coating may prevent the shaped abrasiveparticle from capping. Capping is the term to describe the phenomenonwhere metal particles from the workpiece being abraded become welded tothe tops of the shaped abrasive particles. Surface coatings to performthe above functions are known to those of skill in the art.

Abrasive Article Having Shaped Abrasive Particles with a SlopingSidewall

Referring to FIGS. 1C, 4C, and 5C, a coated abrasive article 40comprises a backing 42 having a first layer of binder, hereinafterreferred to as the make coat 44, applied over a first major surface 41of backing 42. Attached or partially embedded in the make coat 44 are aplurality of shaped abrasive particles 20 with a sloping sidewall 22and/or grooves 116 forming an abrasive layer. Over the shaped abrasiveparticles 20 with a sloping sidewall 22 is a second layer of binder,hereinafter referred to as the size coat 46. The purpose of make coat 44is to secure shaped abrasive particles 20 with n sloping sidewall 22 tobacking 42 and the purpose of size coat 46 is to reinforce shapedabrasive particles 20 with a sloping sidewall 22. The majority of theshaped abrasive particles 20 with a sloping sidewall 22 are orientedsuch that the tip 48 or vertex points away from the backing 42 and theshaped abrasive particles are resting on the sloping sidewall 22 andtipped or leaning as shown.

The make coat 44 and size coat 46 comprise a resinous adhesive. Theresinous adhesive of the make coat 44 can be the same as or differentfrom that of the size coat 46. Examples of resinous adhesives that aresuitable for these coats include phenolic resins, epoxy resins,urea-formaldehyde resins, acrylate resins, aminoplast resins, melamineresins, acrylated epoxy resins, urethane resins and combinationsthereof. In addition to the resinous adhesive, the make coat 44 or sizecoat 46, or both coats, may further comprise additives that are known inthe art, such as, for example, fillers, grinding aids, wetting agents,surfactants, dyes, pigments, coupling agents, adhesion promoters, andcombinations thereof. Examples of fillers include calcium carbonate,silica, talc, clay, calcium metasilicate, dolomite, aluminum sulfate andcombinations thereof.

A grinding aid can be applied to the coated abrasive article. A grindingaid is defined as particulate material, the addition of which has asignificant effect on the chemical and physical processes of abrading,thereby resulting in improved performance. Grinding aids encompass awide variety of different materials and can be inorganic or organic.Examples of chemical groups of grinding aids include waxes, organichalide compounds, halide salts, and metals and their alloys. The organichalide compounds will typically break down during abrading and release ahalogen acid or a gaseous halide compound. Examples of such materialsinclude chlorinated waxes, such as tetrachloronaphthalene,pentachloronaphthalene; and polyvinyl chloride. Examples of halide saltsinclude sodium chloride, potassium cryolite, sodium cryolite, ammoniumcryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, siliconfluorides, potassium chloride, magnesium chloride. Examples of metalsinclude tin, lead, bismuth, cobalt, antimony, cadmium, iron, andtitanium. Other grinding aids include sulfur, organic sulfur compounds,graphite, and metallic sulfides. It is also within the scope of thisinvention to use a combination of different grinding aids; in someinstances, this may produce a synergistic effect. In one embodiment, thegrinding aid was cryolite or potassium tetrafluoroborate. The amount ofsuch additives can be adjusted to give desired properties. It is alsowithin the scope of this invention to utilize a supersize coating. Thesupersize coating typically contains a binder and a grinding aid. Thebinders can be formed from such materials as phenolic resins, acrylateresins, epoxy resins, urea-formaldehyde resins, melamine resins,urethane resins, and combinations thereof.

It is also within the scope of this invention that the shaped abrasiveparticles 20 with a sloping sidewall 22 and/or grooves 116 can beutilized in a bonded abrasive article, a nonwoven abrasive article, orabrasive brushes. A bonded abrasive can comprises a plurality of theshaped abrasive particles 20 bonded together by means of a binder toform a shaped mass. The binder for a bonded abrasive can be metallic,organic, or vitreous. A nonwoven abrasive comprises a plurality of theshaped abrasive particles 20 bonded into a fibrous nonwoven web by meansof an organic binder.

Method of Making Shaped Abrasive Particles with a Sloping Sidewall

The first process step involves providing either a seeded on un-seededabrasive dispersion that can be converted into alpha alumina. The alphaalumina precursor composition often comprises a liquid that is avolatile component. In one embodiment, the volatile component is water.The abrasive dispersion should comprise a sufficient amount of liquidfor the viscosity of the abrasive dispersion to be sufficiently low toenable filling the mold cavities and replicating the mold surfaces, butnot so much liquid as to cause subsequent removal of the liquid from themold cavity to be prohibitively expensive. In one embodiment, theabrasive dispersion comprises from 2 percent to 90 percent by weight ofthe particles that can be converted into alpha alumina, such asparticles of aluminum oxide monohydrate (boehmite), and at least 10percent by weight, or from 50 percent to 70 percent, or 50 percent to 60percent, by weight of the volatile component such as water. Conversely,the abrasive dispersion in some embodiments contains from 30 percent to50 percent, or 40 percent to 50 percent, by weight solids.

Aluminum oxide hydrates other than boehmite can also be used. Boehmitecan be prepared by known techniques or can be obtained commercially.Examples of commercially available boehmite include products having thetrademarks “DISPERAL”, and “DISPAL”, both available from Sasol NorthAmerica, Inc. or “HiQ-40” available from BASF Corporation. Thesealuminum oxide monohydrates are relatively pure, i.e., they includerelatively little, if any, hydrate phases other than monohydrates, andhave a high surface area. The physical properties of the resultingshaped abrasive particles 20 with a sloping sidewall 22 will generallydepend upon the type of material used in the abrasive dispersion.

In one embodiment, the abrasive dispersion is in a gel state. As usedherein, a “gel” is a three dimensional network of solids dispersed in aliquid. The abrasive dispersion may contain a modifying additive orprecursor of a modifying additive. The modifying additive can functionto enhance some desirable property of the abrasive particles or increasethe effectiveness of the subsequent sintering step. Modifying additivesor precursors of modifying additives can be in the form of solublesalts, typically water soluble salts. They typically consist of ametal-containing compound and can be a precursor of oxide of magnesium,zinc, iron, silicon, cobalt, nickel, zirconium, hafnium, chromium,yttrium, praseodymium, samarium, ytterbium, neodymium, lanthanum,gadolinium, cerium, dysprosium, erbium, titanium, and mixtures thereof.The particular concentrations of these additives that can be present inthe abrasive dispersion can be varied based on skill in the art.Typically, the introduction of a modifying additive or precursor of amodifying additive will cause the abrasive dispersion to gel. Theabrasive dispersion can also be induced to gel by application of heatover a period of time.

The abrasive dispersion can also contain a nucleating agent to enhancethe transformation of hydrated or calcined aluminum oxide to alphaalumina. Nucleating agents suitable for this disclosure include fineparticles of alpha alumina, alpha ferric oxide or its precursor,titanium oxides and titanates, chrome oxides, or any other material thatwill nucleate the transformation. The amount of nucleating agent, ifused, should be sufficient to effect the transformation of alphaalumina. Nucleating such abrasive dispersions is disclosed in U.S. Pat.No. 4,744,802 to Schwabel.

A peptizing agent can be added to the abrasive dispersion to produce amore stable hydrosol or colloidal abrasive dispersion. Suitablepeptizing agents are monoprotic acids or acid compounds such as aceticacid, hydrochloric acid, formic acid, and nitric acid. Multiprotic acidscan also be used but they can rapidly gel the abrasive dispersion,making it difficult to handle or to introduce additional componentsthereto. Some commercial sources of boehmite contain an acid titer (suchas absorbed formic or nitric acid) that will assist in forming a stableabrasive dispersion.

The abrasive dispersion can be formed by any suitable means, such as,for example, simply by mixing aluminum oxide monohydrate with watercontaining a peptizing agent or by forming an aluminum oxide monohydrateslurry to which the peptizing agent is added. Defoamers or othersuitable chemicals can be added to reduce the tendency to form bubblesor entrain air while mixing. Additional chemicals such as wettingagents, alcohols, or coupling agents can be added if desired. The alphaalumina abrasive grain may contain silica and iron oxide as disclosed inU.S. Pat. No. 5,645,619 to Erickson et al. on Jul. 8, 1997. The alphaalumina abrasive grain may contain zirconia as disclosed in U.S. Pat.No. 5,551,963 to Larmie on Sep. 3, 1996. Alternatively, the alphaalumina abrasive grain can have a microstructure or additives asdisclosed in U.S. Pat. No. 6,277,161 to Castro on Aug. 21, 2001.

The second process step involves providing a mold having at least onemold cavity, and preferably a plurality of cavities. The mold can have agenerally planar bottom surface and a plurality of mold cavities. Theplurality of cavities can be formed in a production tool. The productiontool can be a belt, a sheet, a continuous web, a coating roll such as arotogravure roll, a sleeve mounted on a coating roll, or die. Theproduction tool comprises polymeric material. Examples of suitablepolymeric materials include thermoplastics such as polyesters,polycarbonates, poly(ether sulfone), poly(methyl methacrylate),polyurethanes, polyvinylchloride, polyolefins, polystyrene,polypropylene, polyethylene or combinations thereof, and thermosettingmaterials. In one embodiment, the entire tooling is made from apolymeric or thermoplastic material. In another embodiment, the surfacesof the tooling in contact with the sol-gel while drying, such as thesurfaces of the plurality of cavities (mold bottom surface and moldsidewall) comprises polymeric or thermoplastic materials and otherportions of the tooling can be made from other materials. A suitablepolymeric coating may be applied to a metal tooling to change itssurface tension properties by way of example.

A polymeric or thermoplastic tool can be replicated off a metal mastertool. The master tool will have the inverse pattern desired for theproduction tool. The master tool can be made in the same manner as theproduction tool. In one embodiment, the master tool is made out ofmetal, e.g., nickel and is diamond turned. A polymeric or thermoplasticsheet material can be heated along with the master tool such that thematerial is embossed with the master tool pattern by pressing the twotogether. A polymeric or thermoplastic material can also be extruded orcast onto the master tool and then pressed. The thermoplastic materialis cooled to solidify and produce the production tool. If athermoplastic production tool is utilized, then care should be taken notto generate excessive heat that may distort the thermoplastic productiontool limiting its life. More information concerning the design andfabrication of production tooling or master tools can be found in U.S.Pat. No. 5,152,917 (Pieper et al.); U.S. Pat. No. 5,435,816 (Spurgeon etal.); U.S. Pat. No. 5,672,097 (Hoopman et al.); U.S. Pat. No. 5,946,991(Hoopman et al.); U.S. Pat. No. 5,975,987 (Hoopman et al.); and U.S.Pat. No. 6,129,540 (Hoopman et al.).

Access to cavities can be from an opening in the top surface or bottomsurface of the mold. In some instances, the cavity can extend for theentire thickness of mold. Alternatively, the cavity can extend only fora portion of the thickness of the mold. In one embodiment, the topsurface is substantially parallel to bottom surface of the mold with thecavities having a substantially uniform depth. At least one side of themold, i.e. the side in which the cavity is formed, can remain exposed tothe surrounding atmosphere during the step in which the volatilecomponent is removed.

The cavity has a specified three-dimensional shape. In one embodiment,the shape of a cavity can be described as being a triangle, as viewedfrom the top, having a sloping sidewall such that the bottom surface ofthe cavity is slightly smaller than the opening in the top surface. Asloping sidewall is believed to enhance grinding performance and enableeasier removal of the precursor abrasive particles from the mold. Inanother embodiment, the mold comprised a plurality of triangularcavities. Each of the plurality of triangular cavities comprises anequilateral triangle.

Alternatively, other cavity shapes can be used, such as, circles,rectangles, squares, hexagons, stars, or combinations thereof, allhaving a substantially uniform depth dimension. The depth dimension isequal to the perpendicular distance from the top surface to thelowermost point on the bottom surface. The depth of a given cavity canbe uniform or can vary along its length and/or width. The cavities of agiven mold can be of the same shape or of different shapes.

The third process step involves filling the cavities in the mold withthe abrasive dispersion by any conventional technique. In someembodiments, a knife roll coater or vacuum slot die coater can be used.A mold release can be used to aid in removing the particles from themold if desired. Typical mold release agents include oils such as peanutoil or mineral oil, fish oil, silicones, polytetrafluoroethylene, zincsterate, and graphite. In general, between about 0.1% to about 5% byweight mold release agent, such as peanut oil, in a liquid, such aswater or alcohol, is applied to the surfaces of the production toolingin contact with the sol-gel such that between about 0.1 mg/in² to about3.0 mg/in², or between about 0.1 mg/in² to about 5.0 mg/in² of the moldrelease agent is present per unit area of the mold when a mold releaseis desired. In one embodiment, the top surface of the mold is coatedwith the abrasive dispersion. The abrasive dispersion can be pumped ontotop surface. Next, a scraper or leveler bar can be used to force theabrasive dispersion fully into the cavity of the mold. The remainingportion of the abrasive dispersion that does not enter cavity can beremoved from top surface of the mold and recycled. In some embodiments,a small portion of the abrasive dispersion can remain on top surface andin other embodiments the top surface is substantially free of thedispersion. The pressure applied by the scraper or leveler bar istypically less than 100 psi, or less than 50 psi, or less than 10 psi.In some embodiments, no exposed surface of the abrasive dispersionextends substantially beyond the top surface to ensure uniformity inthickness of the resulting shaped abrasive particles 20.

The fourth process step involves removing the volatile component to drythe dispersion. Desirably, the volatile component is removed by fastevaporation rates. In some embodiments, removal of the volatilecomponent by evaporation occurs at temperatures above the boiling pointof the volatile component. An upper limit to the drying temperatureoften depends on the material the mold is made from. For polypropylenetooling the temperature should be less than the melting point of theplastic.

In one embodiment, for a water dispersion of between about 40 to 50percent solids and a polypropylene mold, the drying temperatures can bebetween about 90 degrees C. to about 165 degrees C., or between about105 degrees C. to about 150 degrees C., or between about 105 degrees C.to about 120 degrees C. Higher temperatures can lead to the formation oflarger openings but can also lead to degradation of the polypropylenetooling limiting its useful life as a mold.

In one embodiment, a sample of boehmite sol-gel was made using thefollowing recipe: aluminum oxide monohydrate powder (1600 parts) havingthe trade designation “DISPERAL” was dispersed by high shear mixing asolution containing water (2400 parts) and 70% aqueous nitric acid (72parts) for 11 minutes. The resulting sol-gel was aged for at least 1hour before coating. The sol-gel was forced into production toolinghaving triangular shaped mold cavities of 28 mils depth and 110 mils oneach side and having a predetermined draft angel α between the moldsidewall and mold bottom surface of 98 degrees. During manufacture ofthe production tooling, 50% of the mold cavities comprised ridges on themold bottom surface thereby forming the shaped abrasive particles ofFIGS. 3 and 4, and the other 50% of the mold cavities had a smoothbottom surface.

The sol-gel was forced into the cavities with a putty knife so that theopenings of the production tooling were completely filled. A moldrelease agent, 1% peanut oil in methanol was used to coat the productiontooling such that about 0.5 mg/in² of peanut oil was applied to the moldsurfaces. The excess methanol was removed by placing sheets of theproduction tooling in an air convection oven for 5 minutes at 45 C. Thesol-gel coated production tooling was placed in an air convection ovenat 45 C for at least 45 minutes to dry. The precursor shaped abrasiveparticles were removed from the production tooling by passing it over anultrasonic horn. These precursor shaped abrasive particles can be firedto produce shaped abrasive particles 20 with a sloping sidewall 22and/or grooves 116.

The fifth process step involves removing the precursor shaped abrasiveparticles with a sloping sidewall from the mold cavities. The precursorshaped abrasive particles with a sloping sidewall can be removed fromthe cavities by using the following processes alone or in combination onthe mold: gravity, vibration, ultrasonic vibration, vacuum, orpressurized air to remove the particles from the mold cavities.

The precursor abrasive particles with a sloping sidewall can be furtherdried outside of the mold. If the abrasive dispersion is dried to thedesired level in the mold, this additional drying step is not necessary.However, in some instances it may be economical to employ thisadditional drying step to minimize the time that the abrasive dispersionresides in the mold. Typically, the precursor shaped abrasive particleswill be dried from 10 to 480 minutes, or from 120 to 400 minutes, at atemperature from 50 degrees C. to 160 degrees C., or at 120 degrees C.to 150 degrees C.

The sixth process step involves calcining the precursor shaped abrasiveparticles with a sloping sidewall 22. During calcining, essentially allthe volatile material is removed, and the various components that werepresent in the abrasive dispersion are transformed into metal oxides.The precursor shaped abrasive particles are generally heated to atemperature from 400 degrees C. to 800 degrees C., and maintained withinthis temperature range until the free water and over 90 percent byweight of any bound volatile material are removed. In an optional step,it may be desired to introduce the modifying additive by an impregnationprocess. A water-soluble salt can be introduced by impregnation into thepores of the calcined, precursor shaped abrasive particles. Then theprecursor shaped abrasive particles are prefixed again. This option isfurther described in European Patent Application No. 293,163.

The seventh process step involves sintering the calcined, precursorshaped abrasive particles to form alpha alumina particles. Prior tosintering, the calcined, precursor shaped abrasive particles are notcompletely densified and thus lack the desired hardness to be used asshaped abrasive particles. Sintering takes place by heating thecalcined, precursor shaped abrasive particles to a temperature of from1,000 degrees C. to 1,650 degrees C. and maintaining them within thistemperature range until substantially all of the alumina monohydrate (orequivalent) is converted to alpha alumina and the porosity is reduced toless than 15 percent by volume. The length of time to which thecalcined, precursor shaped abrasive particles must be exposed to thesintering temperature to achieve this level of conversion depends uponvarious factors but usually from five seconds to 48 hours is typical. Inanother embodiment, the duration for the sintering step ranges from oneminute to 90 minutes. After sintering, the shaped abrasive particleswith a sloping sidewall can have a Vickers hardness of 10 GPa, 16 GPa,18 GPa, 20 GPa, or greater.

Other steps can be used to modify the described process, such as rapidlyheating the material from the calcining temperature to the sinteringtemperature, centrifuging the abrasive dispersion to remove sludge,waste, etc. Moreover, the process can be modified by combining two ormore of the process steps if desired. Conventional process steps thatcan be used to modify the process of this disclosure are more fullydescribed in U.S. Pat. No. 4,314,827 to Leitheiser. More informationconcerning methods to make shaped abrasive particles is disclosed incopending U.S. patent application Ser. No. 12/337,001 entitled “MethodOf Making Abrasive Shards, Shaped Abrasive Particles With An Opening, OrDish-Shaped Abrasive Particles”, and filed on Dec. 17, 2008.

EXAMPLES

Objects and advantages of this disclosure are further illustrated by thefollowing non-limiting examples. The particular materials and amountsthereof recited in these examples as well as other conditions anddetails, should not be construed to unduly limit this disclosure. Unlessotherwise noted, all parts, percentages, ratios, etc. in the Examplesand the rest of the specification are by weight.

Preparation of REO-Doped Shaped Abrasive Particles

A sample of boehmite sol-gel was made using the following recipe:aluminum oxide monohydrate powder (1600 parts) having the tradedesignation “DISPERAL” was dispersed by high shear mixing a solutioncontaining water (2400 parts) and 70% aqueous nitric acid (72 parts) for11 minutes. The resulting sol-gel was aged for at least 1 hour beforecoating. The sol-gel was forced into production tooling havingtriangular shaped mold cavities of 28 mils depth and 110 mils on eachside. The draft angel α between the mold sidewall and mold bottomsurface was different for each production tooling. The draft angle α was90 degrees for the first tooling, 98 degrees for the second tooling, 120degrees for the third tooling and 135 degrees for the last tooling. The98 degree draft angle production tooling was manufactured to have 50% ofthe mold cavities with 8 parallel ridges rising from the bottom surfacesof the cavities that intersected with one side of the triangle at a 90degree angle and the remaining cavities had a smooth bottom moldsurface. The parallel ridges were spaced every 0.277 mm and the crosssection of the ridges was a triangle shape having a height of 0.0127 mmand a 45 degree angle between the sides of each ridge at the tip asdescribed above. The sol-gel was forced into the cavities with a puttyknife so that the openings of the production tooling were completelyfilled. A mold release agent, 1% peanut oil in methanol was used to coatthe production tooling with about 0.5 mg/in² of peanut oil applied tothe production tooling. The excess methanol was removed by placingsheets of the production tooling in an air convection oven for 5 minutesat 45 degrees C. The sol-gel coated production tooling was placed in anair convection oven at 45 degrees C. for at least 45 minutes to dry. Theprecursor shaped abrasive particles were removed from the productiontooling by passing it over an ultrasonic horn. The precursor shapedabrasive particles were calcined at approximately 650 degrees Celsiusand then saturated with a mixed nitrate solution of the followingconcentration (reported as oxides): 1.8% each of MgO, Y₂O₃, Nd₂O₃ andLa₂O₃. The excess nitrate solution was removed and the saturatedprecursor shaped abrasive particles with openings were allowed to dryafter which the particles were again calcined at 650 degrees Celsius andsintered at approximately 1400 degrees Celsius. Both the calcining andsintering was performed using rotary tube kilns.

After making the shaped abrasive particles with sloping sidewalls havingthe four different draft angles, coated abrasive discs were made. Theshaped abrasive particles with sloping sidewalls and/or grooves 116 wereelectrostatic coated onto a 7 inch diameter fiber disc with a ⅞ inchcenter hole using phenolic make coat and size coat resins as shown inTable 1. The phenolic resin can be made from resole phenol-formaldehyderesin, a 1.5:1 to 2.1:1 (phenol:formaldehyde) condensate catalyzed by 1to 5% potassium hydroxide.

TABLE 1 Make and Size Coat Formulation Ingredient Make Coat Size CoatPhenolic Resin 49.15% 29.42% Water 10.19% 18.12% Calcium Carbonate40.56% 0.0% Cryolite 0.0% 50.65% Emulon A (BASF) 0.10% 1.81% 100.0%100.0%

The grinding performance of the shaped abrasive particles with a slopingsidewall and/or grooves 116 was evaluated by grinding 1045 medium carbonsteel using the following procedure. 7-inch (17.8 cm) diameter abrasivediscs for evaluation were attached to a rotary grinder fitted with a7-inch (17.8 cm) ribbed disc pad face plate (“80514 Extra Hard Red”obtained from 3M Company, St. Paul, Minn.). The grinder was thenactivated and urged against an end face of a 0.75×0.75 in (1.9×1.9 cm)pre-weighed 1045 steel bar under a load of 12 lb (5.4 kg). The resultingrotational speed of the grinder under this load and against thisworkpiece was 5000 rpm. The workpiece was abraded under these conditionsfor a total of fifty (50) 10-second grinding intervals (passes).Following each 10-second interval, the workpiece was allowed to cool toroom temperature and weighed to determine the cut of the abrasiveoperation. Test results were reported as the incremental cut for eachinterval and the total cut removed. If desired, the testing can beautomated using suitable equipment.

Referring to FIG. 11, the Cut Rate versus Time and the Total Cut Ratefor the shaped abrasive particles with a 98 degree draft angle with andwithout grooves is illustrated. As seen, the initial cut rate for theshaped abrasive particles without grooves is greater than for the samesize shaped abrasive particles with grooves. The cut rate for the shapedabrasive particles without grooves tends to decrease as the testprogresses while the cut rate for shaped abrasive particles with groovestends to increase as the test progresses.

Referring to FIGS. 12 and 13, the Cut Rate versus Time and the Total Cutversus Time are plotted. As seen, shaped abrasive particles having asloping sidewall with a draft angle greater than 90 degreessignificantly out performed similarly shaped abrasive particles having a90 degree draft angle. As the draft angle approached 135 degrees, theperformance of the shaped abrasive particles with a sloping sidewallbegin to rapidly deteriorate. When particles having a 135 degree draftangle are compared to the particles having a draft angle of 98 degrees,the initial cut rate was about the same but the total cut wassignificantly reduced. The particles having a draft angle of 120 degreeshad approximately a 20% improvement in initial cut and approximately thesame total cut as particles having a 98 degree draft angle, which wasunexpected. Even more surprising, particles having only an 8 degreeschange in draft angle from 90 degrees to 98 degrees had a huge jump inperformance. The cut rate was approximately doubled and the cut rateremained relatively constant during the entire test duration since theabrasive article was a blend of 50% shaped abrasive particles withgrooves and 50% shaped abrasive particles without grooves.

Other modifications and variations to the present disclosure may bepracticed by those of ordinary skill in the art, without departing fromthe spirit and scope of the present disclosure, which is moreparticularly set forth in the appended claims. It is understood thataspects of the various embodiments may be interchanged in whole or partor combined with other aspects of the various embodiments. All citedreferences, patents, or patent applications in the above application forletters patent are herein incorporated by reference in their entirety ina consistent manner. In the event of inconsistencies or contradictionsbetween portions of the incorporated references and this application,the information in the preceding description shall control. Thepreceding description, given in order to enable one of ordinary skill inthe art to practice the claimed disclosure, is not to be construed aslimiting the scope of the disclosure, which is defined by the claims andall equivalents thereto.

What is claimed is:
 1. A coated abrasive article comprising: shapedabrasive particles and a make coat on a first major surface of abacking, the shaped abrasive particles each having a sidewall, each ofthe shaped abrasive particles comprising alpha alumina and having afirst face and a second face separated by the sidewall and having amaximum thickness, T; a blend of the shaped abrasive particles adheredto the make coat by the sidewall forming an abrasive layer, the abrasivelayer coated with a size coat; the blend of the shaped abrasiveparticles comprises a plurality of shaped abrasive particles having aplurality of grooves on the second face and a plurality of shapedabrasive particles without the plurality of grooves on the second face,and the particles comprise a draft angle α between the second face andthe sidewall and the draft angle α is between 95 degrees to about 130degrees.
 2. The abrasive article of claim 1 wherein the blend of theshaped abrasive particles comprises approximately 40%-60% by weight ofthe shaped abrasive particles with the plurality of grooves andapproximately 40%-60% by weight of the shaped abrasive particles withoutthe plurality of grooves.
 3. The abrasive article of claim 1 wherein theplurality of grooves extend completely across the second face andintersect with a first edge of the second face at a 90 degree angle. 4.The abrasive article of claim 1 wherein the cross sectional geometry ofthe plurality of grooves comprises a triangle or a truncated triangle.5. The abrasive article of claim 1 wherein the plurality of groovescomprises a percent spacing and the percent spacing is between about 1%to about 50%.
 6. The abrasive article of claim 1 wherein each of theplurality of grooves comprises a depth, D, and a percentage ratio of D/Tis between about 0.1% to about 30%.
 7. The abrasive article of claim 1wherein a perimeter of the first face and a perimeter of the second facecomprise an equilateral triangle.
 8. The abrasive article of claim 1wherein the first face is recessed or concave and the second face issubstantially planar.
 9. The abrasive article of claim 1 wherein thefirst face is convex and the second face is concave.
 10. The abrasivearticle of claim 1 wherein the plurality of grooves comprises a crosshatch pattern of intersecting lines.